This invention relates to a cylinder head arrangement for a multi-valve engine, and more particularly to an improved unitary cylinder head casting for an engine.
In internal combustion engines, it is well known that the performance of the engine can be improved by increasing the number of valves per cylinder. For this reason, four valve per cylinder engines are quite common, particularly in high-performance engines. However, the use of five valves per cylinder to improve engine performance is now being widely accepted.
One difficulty with a five valve per cylinder engine is that the cylinder head assembly becomes quite complicated. In addition to the sliding support for the individual valves, normally these engines employ two overhead camshafts per cylinder bank. The valves are directly actuated by thimble tappets that are interposed between the individual camshafts and the valves which they actuate. The tappets and camshafts are also supported by the cylinder head. Because of the complexity of these cylinder head assemblies, it has been frequently the practice to utilize a multi-part cylinder head assembly. However, such multi-part cylinder head assemblies present problems in and of themselves.
With a multi-valve assembly, the individual components of the cylinder head must be machined, and these machined surfaces then must be assembled together. This obviously increases the number of fasteners that must be employed in the head assembly and also makes the placement of the fasteners that fix the head assembly to the block more difficult.
It is, therefore, a principal object of this invention to provide an improved unitary cylinder head for an internal combustion engine.
It is a further object of this invention to provide a unitary cylinder head for a multi-valve twin overhead camshaft internal combustion engine.
It is a further object of this invention to provide a cylinder head for a multi-valve engine, wherein the cylinder head itself reciprocally supports the valves, the tappets that actuate the valves, and the camshafts that operate the tappets.